Teach me the ways of the cam

[andrew.brandon]

Someone posted this link a few months ago about an introduction to cams, http://www.newcovenant.com/speedcraf...camshaft/1.htm I had nothing to do today so I thought I would read it however the link no longer works. got any other links for basic stuff?

[Wicked 3800 V6]

Go to howstuffworks.com

[98Camaro3.8]

http://web.archive.org/web/200402201...camshaft/1.htm

[andrew.brandon]

Originally posted by 98Camaro3.8:
http://web.archive.org/web/200402201...camshaft/1.htm

thanks man.

[oil pan 4]

As for the position of the piston and valve.
On a big cam it start with over lap.
The intake valve opens as much as 15 and some times as much as 20 degrees (20 is more for 14,000rpm motor cycle engines) BTDC.
The exhaust valve closes lets say 8-10 degrees ATDC when the piston is moving down there is still exhaust getting blown out.
At low rpms this is bad. exhaust gets sucked into the intake runner at low rpms while there is vacuum in the intake. To take full advantage of this there must be positive pressure on the intake valve at high rpms when the intake valve starts opening at 15 degrees BTDC There is a slight vacuum in the chamber. because the exhaust valve opened before BDC, letting the exploding gas blowing its self out. but I'm not going to get to far into that yet.
As the intake valve starts really opening with the piston at 5-8 degrees (I mean open enough to let some air move) BTDC. There is intake air being sucked in and getting forced into the chamber chasing out the exhaust while the piston is moving up in the cylinder.
As both valves are open there most (about 1/16'') at the same time and the piston is at TDC the exhaust is sucking all of its self out and the intake air is starting to force its self and it is taking over.
Once the exhaust valve closes all the way the intake air is trapped and the piston is moving down.
The intake valve is open its most well after 90 ATDC. Its open it's most around 30-50 degrees before BDC depending on if its a big turbo cam or big N/A cam.
And closes as late as 40 degrees ABDC (don't think I have seen any that close later than that), that is when most of the air is sucked into the cylinder (ABDC). Yes there is a lot of air still getting sucked into the chamber because the runner air was accelerated during the time when the piston was between around 90 ATDC and full valve open. So now that the piston is moving up and air is getting into the chamber by means of some unseen force.
At this point the engine is super charging its self. The amount of self super chagrined is determined by a lot of factors, rpm, runners, intake harmonics, valve timing (mainly intake open ABDC), spark timing comes into play a lot when you do FI and more.
The self super charging really starts with the exhaust opening well before BDC on the power stroke and the exhaust blows its self out creating a slight vacuumed sucking the piston up the bore and some times contaminating the chamber with oil if you don't.
Hope this helps some.

[malice10985]

http://www.camarov6.com/ubb/ultimate...=002798#000000

It's not cam theory, but it talks about 3800 cams. I guess that is useless to you though, since you have a 3.4L.